1. Field of the Invention:
The present invention relates generally to the production of closures for fly openings, and more particularly to a method and apparatus for sewing successive individual fly pieces one after another to a continuous slide fastener chain.
2. Description of the Prior Art
Various methods and apparatus for automatically or semi-automatically sewing individual fly pieces to a continuous slide fastener chain are known, such as exemplified in U.S. Pat. Nos. 4,362,116; 4,236,292; 4,152,996; and 4,576,104.
For attachment, the individual fly pieces are fed successively to a sewing station in underlying relation to the continuous slide fastener chain while they are kept in a closely spaced end-to-end relation. The fly pieces preferably have an elongate rectangular shape because owing to its rectangular shape, the leading end of each succeeding fly piece is able to abut in end-to-end relation to the trailing end of the preceding fly piece, thus assuring formation of a closely spaced end-to-end train of individual fly pieces while they are fed. The rectangular fly pieces are therefore widely used as shown, for example, in the above-mentioned U.S. Pat. Nos. 4,362,116 and 4,236,292.
However, such rectangular fly pieces encounter difficulties when they are attached to the trousers. As illustrated here in FIG. 8 of the accompanying drawings, when a rectangular fly piece 10 with a slide fastener 11 attached thereto is sewn to the front 12 of a pair of trousers by means of two lines of ornamental stitches, so-called "J-stitches" 13, a substantially triangular flap 14 is produced on the outside of the J-stitches 13. The triangular flap 14 is unsightly in appearance, makes the trousers appear unsightly and provides a sense of discomfort for the wearer, thereby limiting the use of the rectangular fly pieces. The formation of the triangular flap 14 can be avoided by sewing the rectangular fly piece 10 with the J-stitches 13 to the trousers front 12 while an outer corner of the rectangular fly piece 10 is being folded manually by an operator. Such sewing operation is tedious and time-consuming, requires a great deal of skill and considerably lowers the sewing efficiency. Furthermore, the J-stitches 13 are likely to run irregularly, resulting in a low product value.
Fly pieces used in the sewing operation shown in the aforesaid U.S. Pat. No. 4,152,996 have a curvature at the leading end as they are previously trimmed at one edge so as to conform a path of movement of the J-stitches. Such fly pieces can be neatly stitched to the trousers fronts with utmost ease. However, the fly pieces having such curved leading ends are likely to be displaced irregularly as they are conveyed toward a sewing station for attachment to a continuous slide fastener chain, with the result that the fly pieces joined by the slide fastener chain are disposed out of alignment with the slide fastener chain.
The prior art, as exemplified in the above-mentioned U.S. Pat. No. 4,576,104 and 4,362,116 contains a fly feed unit consisting of a series of opposed driven roller and idle support roller pairs or an endless belt conveyor which is disposed upstream of a sewing station for forcibly supplying fly pieces successively into the sewing station in underlying relation to a continuous slide fastener chain. Then, the fly pieces and the fastener chain are moved through the sewing station by means of a feed dog and a presser foot cooperating therewith as the stitching advances.
The conventional feed unit operates satisfactorily when the fly pieces are formed of a relatively thick and sturdy cloth such as denim. An accurate and reliable fly-piece feeding cannot be achieved however when the conventional feed unit is used with fly pieces of a relatively thin and flexible cloth because such relatively thin and flexible fly pieces are likely to overlap or become wavy as they are forced by the feed unit into the sewing station.